Scientists have long observed a link between cigarette smoking and depression, and questions over which causes which--or whether both are caused by some third factor--have abounded. Now a study in adolescents has found that heavy smoking and depression affect each other reciprocally, creating a self-perpetuating pattern of unhealthy behavior and negative effect.
In their research, psychologist Michael Windle, PhD, and colleague Rebecca C. Windle, both of the University of Alabama at Birmingham, studied 1,218 high school students for one and a half years, beginning when the students were sophomores and juniors. Every six months, students completed questionnaires that assessed depression and cigarette smoking as well as variables such as temperament, parents' smoking habits, social support within the family, delinquent activity, alcohol and other substance use, and friends' alcohol and drug use.
The results, published in the April Journal of Consulting and Clinical Psychology (Vol. 69, No. 2), revealed that teen-agers who were heavy smokers at the beginning of the study were more likely to grow more depressed over time than were those who smoked less heavily or not at all. This relationship held even when other factors that could potentially explain the connection were accounted for.
Likewise, the researchers found, teens who had persistent depressive symptoms at the beginning of the study were more likely to increase smoking than were students who were not depressed--again, even when other factors were taken into consideration.
The cycle of depressed effect and smoking behavior may be especially pronounced in young people, Michael Windle maintains, because as a group they are more likely than adults to experience depressive symptoms and to take up smoking as a way to "self-medicate." By altering neurochemical pathways in the brain, studies have indicated, nicotine tweaks the brain's pleasure centers, enhancing mood.
Over time, however, tolerance to nicotine develops and it takes more nicotine to achieve the same effects. Once this cycle has been established, argues Windle, heavy smokers who try to quit are all the more likely to experience depressed mood--and thus to relapse to smoking. That "negative spiral," he suggests, has important implications for smoking-cessation treatment--for adolescents or adults.
"We know that smoking cessation is very difficult to attain, and that people often have relapses on multiple occasions," says Windle. "Treatment programs need to take into account the associated depressed effect that's likely to occur with smoking cessation and take steps to help people cope with it."
NOTE: Each point plotted is the mean of the specified year and the previous year. Hispanic data are derived from self-reports. Heavy tobacco use is daily in the past 30 days. SOURCE: Johnston LD, O'Malley PM, Bachman JG. National Survey Results on Drug Use from the Monitoring the Future Study. 1975-1999. Volume 1: Secondary School Students. Rockville, MD: National Institute on Drug Abuse, 2000. Table D-49, p. 464.